Mid-IR and VUV Spectroscopic Characterisation of Thermally Processed and Electron Irradiated CO2 Astrophysical Ice Analogues

• Published in: arXiv.org
• Main Authors: Mifsud, D V, Kaňuchová, Z, Ioppolo, S, Herczku, P, Muiña, A Traspas, Field, T A, Hailey, P A, Juhász, Z, Kovács, STS, Mason, N J, McCullough, R W, Pavithraa, S, Rahul, K K, Paripás, B, Sulik, B, Chou, S L, Lo, JI, Das, A, Cheng, B M, Rajasekhar, B N, Bhardwaj, A, Sivaraman, B
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 06.03.2022
• Subjects: Absorption spectra; Annealing; Astrochemistry; Carbon dioxide; Chemical reactions; Chemical synthesis; Comets; Data acquisition; Electron irradiation; Ice; Infrared spectroscopy; Interstellar chemistry; Interstellar matter; Organic chemistry; Physics - Astrophysics of Galaxies; Physics - Chemical Physics; Physics - Earth and Planetary Astrophysics; Physics - Instrumentation and Methods for Astrophysics; Physics - Space Physics; Space telescopes; Spaceborne telescopes; Temperature
• DOI: 10.48550/arxiv.2203.02847

The astrochemistry of CO2 ice analogues has been a topic of intensive investigation due to the prevalence of CO2 throughout the interstellar medium and the Solar System, as well as the possibility of it acting as a carbon feedstock for the synthesis of larger, more complex organic molecules. In order to accurately discern the physico-chemical processes in which CO2 plays a role, it is necessary to have laboratory-generated spectra to compare against observational data acquired by ground- and space-based telescopes. A key factor which is known to influence the appearance of such spectra is temperature, especially when the spectra are acquired in the infrared and ultraviolet. In this present study, we describe the results of a systematic investigation looking into: (i) the influence of thermal annealing on the mid-IR and VUV absorption spectra of pure, unirradiated CO2 astrophysical ice analogues prepared at various temperatures, and (ii) the influence of temperature on the chemical products of electron irradiation of similar ices. Our results indicate that both mid-IR and VUV spectra of pure CO2 ices are sensitive to the structural and chemical changes induced by thermal annealing. Furthermore, using mid-IR spectroscopy, we have successfully identified the production of radiolytic daughter molecules as a result of 1 keV electron irradiation and the influence of temperature over this chemistry. Such results are directly applicable to studies on the chemistry of interstellar ices, comets, and icy lunar objects and may also be useful as reference data for forthcoming observational missions.